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RETRAINING AND DETRAINING IN THE LHC

LHC Machine Advisory Committee , CERN 26 th October 2009. RETRAINING AND DETRAINING IN THE LHC. E. Todesco Magnets , Superconductors and Cryostats Group Technology Department, CERN.

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RETRAINING AND DETRAINING IN THE LHC

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  1. LHC Machine AdvisoryCommittee, CERN 26thOctober 2009 RETRAINING AND DETRAINING IN THE LHC E. Todesco Magnets, Superconductors and Cryostats Group Technology Department, CERN • Acknowledgements: C. Lorin, A. Musso, A. Siemko, L. Rossi,A. Verweij, and all the colleagues involved in manufacturing, testing and commissioning

  2. CONTENTS • Available data • Forecast to 7 TeV • MonteCarlo • Previousestimates • Extrapolation • The Firm3 anomaly • Virgin cycle • Detrainingafter thermal cycle • Analysis • Homogeneity of the production • Correlations vs storage time • Correlations vs elasticmodulus

  3. THE AVAILABLE DATA FROM HARDWARE COMMISSIONING • Sector 5-6 has been trained up to 6.6 TeV • First quenchat 10 kA, 700 A gainedrapidly (5 quenches) • Then a slow training all in Firm3 magnets • Only one magnetquenchedtwice (perhaps), only one detraining • Rememberthat in thissector 55% are from Firm3, but … Training in 5-6 during hardware commissioning

  4. THE AVAILABLE DATA FROM HARDWARE COMMISSIONING • Othersectors: • 5 TeV (8.46 kA) – all sectorswent to thisenergywihtoutquenches • 5.5 TeV (9.31 kA) – 6 sectorswent to thisenergywith 1 quench • 6 TeV(10.16 kA) – 2 sectors(4-5 and 5-6) wentto thisenergywith3 quenches • 6.5 TeV(11.0 kA) – 1 sector (5-6) went to thisenergywith17 quenches

  5. CONTENTS • Available data • Forecast to 7 TeV • MonteCarlo • Previousestimates • Extrapolation • The Firm3 anomaly • Virgin cycle • Detrainingafter thermal cycle • Analysis • Homogeneity of the production • Correlations vs storage time • Correlations vs elasticmodulus

  6. FORECAST BASED ON SURFACE TEST DATA: MONTECARLO ON 5-6 • MonteCarlomethodbased on surface test data (SM18): • For each 5-6 magnet: • Take the first virginquenchmeasured in surface (available for all) • Add the correlationwith the quenchafter a thermal cycle, as measured on the 138 dipolestested in surface, split per Firm • This correlation has a linear part, plus a random one, thisiswhyyouneed a MonteCarlo Correlationbetween 1stvirginquench and 1st quenchafter thermal cycle measured in 138 dipoles [B. Bellesia, N. Catalan Lesheras, E. Todesco, Chamonix 2009]

  7. FORECAST BASED ON SURFACE TEST DATA: MONTECARLO ON 5-6 • MonteCarlomethodbased on surface test data:  Gives the first quenchlevel(10 kA)  Accounts of the factthattraining isdominated by Firm3 in the range 10-11 kA, with a bit of Firm2 and nothingfrom Firm1  Overestimateslevelreachedafter 26 quenchby 500 A  Slopeisdifferent!! MonteCarloforecast for 5-6 and hardware commissioning data [B. Bellesia, N. Catalan Lesheras, E. Todesco, Chamonix 2009]

  8. FORECAST BASED ON SURFACE TEST DATA: MONTECARLO EXTENDED TO THE LHC • MonteCarlomethod: • For 5-6 to reach nominal: 5 quenchesfrom Firm1, 15 from Firm2, 35 from Firm3 • Correcting for the composition of 5-6, weget 400 quenches to reach nominal for the LHC, or 50 quenches per octant

  9. FORECAST BASED ON SURFACE TEST DATA: COMPARISON WITH PREVIOUS ESITMATES • Previousestimates to reach nominal in the tunnel • SCALING-1 HYPOTHESIS: Applying the 80% reduction to the wholesample 0.2 quenchesneeded to go to nominal  30 quenches per octant [P. Pugnat, A. Siemko, IEEE Trans. Appl. Supercond.17 (2007) 1091]

  10. FORECAST BASED ON SURFACE TEST DATA: COMPARISON WITH PREVIOUS ESITMATES • On the other hand … • SCALING-2 HYPOTHESIS: assumingthat all magnetsafter thermal cycle behave as the sampledones  0.35 quenches per octant to reach nominal applies to the LHC  50 quenches to reach nominal [C. Lorin, A. Siemko, E. Todesco, A. Verweij, MT-21 IEEE Trans. Appl. Supercond.20 (2010) to bepublished]

  11. FORECAST BASED ON HARWARE COMMISSIONING DATA: EXTRAPOLATION • Empirical extrapolation of hardware commissioning data based on exponentialfit (verypessimistic) • ~200 quenches per sector 5-6 • For genericsectorhaving 33% of Firm3: 110±35 quenches per octant to reach nominal [A. Verweij, Chamonix 2009] The exponential fit of current vs quenchnumber for 5-6 hardware commissioning

  12. FORECAST: SUMMARY • For 6.5 TeV, a short training isexpected(10-15 quenches per octant) • Needed time: a few days of training per sector • Last method: MonteCarlo for Firm1 and Firm2, plus total loss of memory of Firm3 • Remember Firm3 took 1 quench per magnet to go to 7 TeV in virgin conditions • Estimate= 72 (Firm1)+155 (Firm2)+416 (Firm3)=640 quenches = 80 quenches per octant • Summary training to 7 TeV

  13. CONTENTS • Available data • Forecast to 7 TeV • MonteCarlo • Previousestimates • Extrapolation • The Firm3 anomaly • Virgin cycle • Detrainingafter thermal cycle • Analysis • Homogeneity of the production • Correlations vs storage time • Correlations vs elasticmodulus

  14. THE FIRM3 ANOMALY • Firm3 anomalies in quenchperfomancewere visible in twodifferent aspects in surface test data • (1) Virgin training: Firm3 isdominating the training atlowfields • Around 10 kA, Firm3 quenches are more numerousthan Firm2 and Firm1 • But the Firm3 magnetswere the first to reachultimate! This iswhytheyhad a lot of bonus Cumulated performance of the dipolesduringvirgin training [B. Bellesia, N. Catalan Lesheras and E. Todesco, Chamonix 2009]

  15. THE FIRM3 ANOMALY • Firm3 anomalies in quenchperfomancewere visible in twodifferent aspects in surface test data • (2) De-training after thermal cycle • On the 138 magnetstestedafter thermal cycle, Firm3 is the only one showing more detraining, and net lossafter thermal cycle in a few cases Correlationbetweenlevel of the first virginquench and gain after thermal cycle

  16. THE FIRM3 ANOMALY • Nevertheless, during hardware commissioning the Firm3 detrainingwasmuchworse • Please note: plot is not fair, we compare a distribution of 84 magnets(balls) in 5-6, unveiled up to the dotted line, with a distribution of 36 magnetstestedafter thermal cycle (crosses) Correlationbetweenlevel of the 1st quench and gain after thermal cycle, Firm3 magnets, and hardware commissioning data

  17. A FIRM3 ANOMALY ? • An additional « strangeness » of Firm3 (w.r.t. Firm1 and Firm2): location of the second quench • 95%-100% of the 1stquenchis in the heads, in all firms • 10% of the 2ndquenchis in the straight part for Firm1 and Firm2, 2% only for Firm3 • Is this relevant ? • Doesitmeanthat Firm3 has worseheads or thatit has a better straight part ? Average and stdev of first and second virginquenches, and fraction of them in the heads (measured on a sample) [courtesy of C. Lorin]

  18. CONTENTS • Available data • Forecast to 7 TeV • MonteCarlo • Previousestimates • Extrapolation • The Firm3 anomaly • Virgin cycle • Detrainingafter thermal cycle • Someanalysis • Homogeneity of the production • Correlations vs storage time • Correlations vs elasticmodulus

  19. ANALYSIS: HOMOEGENITY • 1st question: are Firm3 magnets in 5-6 anomalousw.r.t. the whole Firm3 production? • No, the cumulated training of Firm3 magnets in 5-6 isverysimilar to the whole batch Cumulated performance of virgin training of all Firm3 magnets, and of Firm3 magnets in 5-6

  20. ANALYSIS: HOMOEGENITY • 1st question: are Firm3 magnets in 5-6 anomalousw.r.t. the whole Firm3 production? • But itistruethatthere has been a degradationalong the production: first 100 very good, thanworse • 5-6 contains a specific batch, mainlymagnetsfrom 3300 to 3400 Firm3 magnetsinstalled in 5-6 Cumulatedvirgin training of Firm3 magnets, split in four batches [courtesy of C. Lorin]

  21. ANALYSIS: HOMOEGENITY • 2nd question: isthisdetraining due to storage time ? • There isno indication of a correlationwithstorage time Storage time for magnets in 5-6 versus quenchedmagnets [courtesy of A. Musso and C. Lorin]

  22. ANALYSIS: HOMOEGENITY • 3nd question: isthis due to softercoils ? • There is no indication of a correlationwithmeasuredelasticmodulus Elasticmodulus of coils for magnets in 5-6, inner layer [courtesy of A. Musso and C. Lorin]

  23. ANALYSIS: HOMOEGENITY • 3nd question: isthis due to softercoils ? • There is no indication of a correlationwithmeasuredelasticmodulus Elasticmodulus of coils for magnets in 5-6, outer layer [courtesy of A. Musso and C. Lorin]

  24. CONCLUSIONS AND ACTIONS • LHC Energy: • 6.5 TeVisat hand with a verylimited training, a few days per sector • 7 TeVwillneed more training - we have no data! • HC commissioning data of othersectorswill not come before 1 year • Causes of Firm3 anomaly are underanalysis • Evidence of anomalies in surface test data: • Slow training atlowfields and detrainingafter thermal cycle , • But thisis not the whole story!

  25. CONCLUSIONS AND ACTIONS • Actions • Continue the analysis of correlationswith production parameters • One couldmake an extensive campaign of quenchesover several thermal cycles on 2 magnets per Firm, withquench location [proposalfrom G .De Rijk] • After the incident thisis possible, before all Firm3 magnetswere in the tunnel  • But … • One couldrisk to damage the spares • The statisticscouldbe not significant • The magnetsfrom Firm3 come out of the incident  one wouldkeep the doubt of a bias

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